In recent years, high speed and high resolution printing is demanded for ink-jet system printers. Semiconductor processes for silicon substrates, which are microfabrication technologies in the micromachine fields, are applied to the forming method of ink-jet system recording heads employed in the above printers. Consequently, many methods have been proposed which form fine-structured bodies via applying etching onto silicon substrates. Of these, known is a method to form nozzles of an ink-jet system head in such a manner that a silicon substrate is subjected to the following types of etching.
(1) A resist film is formed on the surface of a single crystalline silicon substrate and a first open pattern is formed by removing the portion of the resist film corresponding to the back-end side of the nozzle, while a second open pattern is formed which is smaller than the first open pattern by removing the portion of the resist film corresponding to the tip side of the nozzle, and anisotropic dry etching is applied to the exposed portion of the silicon single crystal substrate surface exposed by the first and second open patterns, whereby nozzles are formed which result in a decrease of the cross section from the back-end side to the tip side (refer to Patent Document 1).(2) A small cross-sectional nozzle is formed from one side of the silicon substrate via dry etching and a part of a large cross-sectional nozzle and a part of a cross-section of an ink chamber provided with an ink chamber communicated with the large cross-sectional nozzle, a pressurizing chamber, and an ink feeding channel are subjected to dry etching from the other side of the silicon substrate to communicate with the small cross-sectional nozzle, whereby a nozzle is formed (refer to Patent Document 2).(3) A buffer layer, which exhibits a lower etching rate compared to a single crystal silicon wafer, is sandwiched between two single crystal silicon wafers to result in integration via close adhesion and both sides of the integrated two single crystal silicon wafers are subjected to etching so that the bottom portion forms holes, each of which reaches the buffer layer. Thereafter, etching is applied to the side on which the bottom diameter of the hole of the buffer layer is smaller, whereby a nozzle hole is formed (refer to Patent Document 3).
Further, characteristics of the surface of the nozzle plate, where the nozzles are formed, affect ejection characteristics of ink droplets. For example, when ink adheres to the periphery of the ejection hole of the nozzle plate to generate non-uniform ink puddles, problems occur in which, for example, when non-uniform ink puddles are generated via adhesion of the ink at the periphery of the ejection hole of the nozzle plate, the ejection direction of ink droplets is bent, the ink droplet size fluctuates, and the flying rate of ink droplets become unstable.
Consequently, as described in Patent Document 4, a technology is known in which forms a liquid repellent treatment on the side of the nozzle plate liquid ejection direction.
According to Patent Document 4, fluorosilane, having at least one hydrolyzable group and silicon atoms bonded to an organic group having at least one fluorine, is applied onto the ejection surface of a liquid ejection head, followed by thermal treatment. Thereafter, a surface treatment is carried out to remove any residual fluorosilane. By carrying out the above surface treatment, a liquid repellent film is formed on the edge surface of the liquid ejection head, whereby it becomes possible to minimize the above drawbacks due to adhesion of ink droplets near the ejection hole.
Further, when nozzle forming members which form a nozzle hole are resinous materials, in order to enhance adhesion of the above liquid repellent film, a technology is known in which an SiO2 film is formed between the nozzle forming member and the liquid repellent film (refer, for example, to Patent Document 5). A nozzle plate which is formed by employing an SiO2 film as an intermediate layer, as described above, results in higher adhesion of the liquid repellent film and exhibits higher resistance to rubbing such as wiping.    Patent Document 1: Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP-A) No. 11-28820    Patent Document 2: JP-A No. 2004-106199    Patent Document 3: JP-A No. 6-134994    Patent Document 4: JP-A No. 5-229130    Patent-Document 5: JP-A No. 2003-341070